Pressure transducers are used in numerous industries, including refineries, other chemical industries, aircraft, automobiles, space travel, etc. A serious problem with pressure transducers is that they need to be calibrated at regular intervals to ensure accurate operation. This usually involves the removal of the transducer from the process being monitored, and taking the transducer to a calibration facility where a series of pressures is applied to the device and its response is compared to the nominal or previous calibration curve. This process will give a certain degree of confidence that the transducer was working during the period since the last calibration, but does not ensure that the transducer will work properly at any time in the future. The removal and calibration is expensive, and the process is either without a measurement during this time or a replacement transducer is installed. Either way, additional costs are incurred either as down time, or the cost of additional transducers.
Various technologies involving pressure transducers have been previously disclosed. For example, U.S. Pat. No. 6,298,731, issued to Wade et al., is directed toward a pressure sensor and regulator for direct injection engine fuel systems. The system combines a pressure transducer with a solenoid valve in order to allow direct control of the fuel line pressure. However, the issue of calibration of the transducer is not disclosed.
U.S. Pat. No. 6,029,524, issued to Klauder et al., discloses a pressure transducer having a redundant fluid pressure sensor which can be used to determine whether the transducer needs to be recalibrated. Similarly, U.S. Pat. No. 5,672,808, issued to Klauder et al., discloses a pressure transducer having a redundant fluid pressure sensor that can be used to determine if the pressure transducer needs to be recalibrated. Two readings from separate sensors are compared to indicate whether they may be an error in one, however, no embedded calibration system is suggested.
U.S. Pat. No. 6,012,336, issued to Eaton et al., discloses a micro electro-mechanical capacitance pressure sensor integrated with electronic circuitry on a common substrate. Again, no calibration system is suggested.
U.S. Pat. No. 5,377,524, issued to Wise et al., discloses a self-testing capacitive pressure transducer. However, this disclosure only pertains to low range capacitive pressure transducers, and does not teach or suggest a calibration system as described herein.
Thus, there is a need to develop a pressure transducer having a built in calibration device capable of generating a series of pressures to thoroughly calibrate the device without removing it from the process. Such a calibration system could also be activated whenever the operation of the transducer is in question, as well as for routine calibration.